Thermal stabilities, physical and optical properties of (KO)-O-2-(NaO)-O-2-(NbO5)-O-2-TeO2 glasses

Abstract

The thermal stabilities, physical and optical properties of xK(2)O-(14-x)Na2O-14Nb(2)O(5)-72TeO(2) (x = 0 similar to 12 mol%) glasses have been studied. The glasses consisting of ca. 10 mol% K2O show high thermal stabilities with values of Delta T = Tx - Tg = ca. 105 degrees C against crystallization, where Tg and Tx are the glass transition and crystallization onset temperatures, respectively. The activation energy of grain growth of a cubic crystalline phase in the 10K(2)O-4Na(2)O-14Nb(2)O(5)-72TeO(2) glass was 7.92 kJ/mol. The energy required for the phase transformation from the 10K(2)O-4Na(2)O-14Nb(2)O(5)-72TeO(2) glass to the cubic crystalline phase was 190.74 kJ/mol. The optical and physical properties of the K2O-Na2O-Nb2O5-TeO2 glasses were obtained: refractive index, n = 1.88-1.97; rho = 4.22-4.64 g/cm(3); optical energy band of the transmission cut-off wavelength, Eg (eV) = 3.17-3.14; relative permittivity, epsilon(r,) = 28-29. The values of R-M and alpha(m) for K2O-Na2O-Nb2O5-TeO2 glasses were much larger than those of Na2O-Nb2O5-TeO2 glasses.